Potato Late Blight Disease Research Articles

A sulfur-containing volatile emitted by potato-associated bacteria confers protection against late blight through direct anti-oomycete activity

Plant diseases are a major cause for yield losses and new strategies to control them without harming the environment are urgently needed. Plant-associated bacteria contribute to their host’s health in diverse ways, among which the emission of disease-inhibiting volatile organic compounds (VOCs). We have previously reported that VOCs emitted by potato-associated bacteria caused strong in vitro growth inhibition of the late blight causing agent Phytophthora infestans. This work focuses on sulfur-containing VOCs (sVOCs) and demonstrates the high in planta protective potential of S-methyl methane thiosulfonate (MMTS), which fully prevented late blight disease in potato leaves and plantlets without phytotoxic effects, in contrast to other sVOCs. Short exposure times were sufficient to protect plants against infection. We further showed that MMTS’s protective activity was not mediated by the plant immune system but lied in its anti-oomycete activity. Using quantitative proteomics, we determined that different sVOCs caused specific proteome changes in P. infestans, indicating perturbations in sulfur metabolism, protein translation and redox balance. This work brings new perspectives for plant protection against the devastating Irish Famine pathogen, while opening new research avenues on the role of sVOCs in the interaction between plants and their microbiome.

Field application of Bacillus subtilis isolates for controlling late blight disease of potato caused by Phytophthora infestans

Abstract Field studies on the biocontrol activity of four B. subtilis isolates viz., B. subtilis MTCC-2422 (T-3), B. subtilis KU936344 (T-4), B. subtilis KU936345(T-5) and B. subtilis KU936341 (T-6), against late blight disease of potato caused by fungus like-organism Phytophthora infestans were investigated. These isolates produce mycotoxins against the causal organism. The fungicide (Mancozeb) M 45 (CURZATE®) was used as positive control. Potato (Solanum tuberosum) cultivar, Kufri Jyoti was used. The treatments were utilized as soil drenching as well as foliar spray. Results reveal that, bacterial treatments significantly reduced disease incidence of late blight compared with the control. Bacterial treatments increased the plant vegetative parameters like plant height, sprouting, number of leaves, fresh weight and dry weight of plants. In addition, treatments also showed the clear difference between commercial and non-commercial tuber yield/hectare. In this experiment, two observations displayed the reduction of the disease severity. There was 32.73% increase in the control plot and 14.3% in chemical fungicide, while in bacterial treatments there was 12.75%, 14.09%, 4.7% and 4.13% increase in the T3, T4, T5 and T6, respectively. Soil drenching of bacterial culture gave the high yield in commercial potato tubers, even when compared with the chemical fungicide. The total yield of control block was 166.04 quintals/hectare but non-commercial yield was 101.07 quintals/hectare. In chemical fungicide, total yield was 188.8 quintals/hectare and non-commercial tubers was 69.66 quintals. The bacterial treatments T4, T5, T6, showed less non-commercial potato yield 48.29, 22.60 and 24.67 quintals/hectare in the total yield of 177.02, 212.89 and 190.737 quintals/hectare in respective treatments. So this study uncovers that B. subtilis treatments are effective under field condition for the control of potato late blight.

First report of the EU_33_A2 clonal lineage of Phytophthora infestans causing late blight disease of potato in Nigeria

Potato (Solanum tuberosum) cultivation was introduced into Nigeria in the Jos Plateau in the early 20th century (Zemba et al., 2013) The Jos Plateau is at high altitude, c. 1,200 m above sea level, and has a cool climate favourable for the …

Managing the Menace of Late Blight Disease of Potato Using Field Resistance in Jos Plateau, Nigeria

Late blight disease caused by Phytophthora infestans is the most destructive of all potato diseases and is recorded as responsible for the famous global famine in the middle of the 19th century in Ireland. It affects leaves, stems and tubers in the field and can absolutely destroy the crop producing up to 100% crop loss. Jos Plateau is noted for favourable cultivation of potato which is an economic crop grown in over 250,000 hectares of land area annually. However, this prospect is hindered by the ravaging late blight which has led to colossal losses in the past three years. Reports from current production suggests great loss has already been recorded this year; so far about 30% of the total harvest is lost due to the severity of the disease. Though farmers attempt to control late blight by spraying fungicides, the use of resistant varieties in combination with other control measures such as proper cultural management and growing potato outside the blight danger period is still the best approach and feasible to small scale farmers. A research was carried out in Kuru (a location in Jos-Plateau well noted for late blight attacks). Sixteen (16) advance varieties and clones from CIP were used to screen for their resistance

Transgenic RXLR Effector PITG_15718.2 Suppresses Immunity and Reduces Vegetative Growth in Potato

Phytophthora infestans causes the severe late blight disease of potato. During its infection process, P. infestans delivers hundreds of RXLR (Arg-x-Leu-Arg, x behalf of any one amino acid) effectors to manipulate processes in its hosts, creating a suitable environment for invasion and proliferation. Several effectors interact with host proteins to suppress host immunity and inhibit plant growth. However, little is known about how P. infestans regulates the host transcriptome. Here, we identified an RXLR effector, PITG_15718.2, which is upregulated and maintains a high expression level throughout the infection. Stable transgenic potato (Solanum tuberosum) lines expressing PITG_15718.2 show enhanced leaf colonization by P. infestans and reduced vegetative growth. We further investigated the transcriptional changes between three PITG_15718.2 transgenic lines and the wild type Désirée by using RNA sequencing (RNA-Seq). Compared with Désirée, 190 differentially expressed genes (DEGs) were identified, including 158 upregulated genes and 32 downregulated genes in PITG_15718.2 transgenic lines. Eight upregulated and nine downregulated DEGs were validated by real-time RT-PCR, which showed a high correlation with the expression level identified by RNA-Seq. These DEGs will help to explore the mechanism of PITG_15718.2-mediated immunity and growth inhibition in the future.

The Effectiveness of Induced Defense Responses in a Susceptible Potato Genotype Depends on the Growth Rate of Phytophthora infestans.

Phytophthora infestans causes the devastating potato late blight disease, which is widely controlled with fungicides. However, the debate about chemical control is fueling a promotion toward alternative methods. In this context, the enhancement of natural plant immunity could be a strategy for more sustainable protection. We previously demonstrated that a concentrated culture filtrate (CCF) of P. infestans primes defense reactions in potato. They are genotype-dependent and metabolites produced decrease pathogen growth in vitro but not in vivo on tubers. Induced potato defenses are assumed to affect P. infestans life history traits depending on strains. This assumption was studied in vivo through induced leaflets on a susceptible genotype inoculated with four P. infestans strains differing for lesion growth rate. This study combines both defenses mechanistic analysis and ecological observations. Defense-gene expressions were thus assessed by quantitative reverse transcription-polymerase chain reaction; pathogen development was simultaneously evaluated by measuring necrosis, quantifying mycelial DNA, and counting sporangia. The results showed that CCF pretreatment reduced the pathogenicity differences between slow- and fast-growing strains. Moreover, after elicitation, PR-1, PR-4, PAL, POX, and THT induction was strain-dependent. These results suggest that P. infestans could develop different strategies to overcome plant defenses and should be considered in biocontrol and epidemic management of late blight.

Simple and inexpensive long-term preservation methods for Phytophthora infestans

Phytophthora infestans is one of the most notorious pathogen among Phytophthora species causing potato late blight disease. Stable and long-term preservation of this pathogen is essential for biological research and fungicide screening. The aim of this study was to find a suitable long-term preservation method for P. infestans. We adjusted the storage temperature, made a slight modification to the rye seed method, and compared the influence of four preservation methods (the mineral oil method, the sterile water method, the rye seed method, and the modified rye seed method) on survival, growth and virulence of four isolates of P. infestans. The results showed that all four methods maintained high viability of the tested P. infestans isolates, but the two rye seed methods were the best ways to maintain 100% viability of the P. infestans isolates without contamination. The four preservation methods did not significantly influence growth or morphological characteristics of the P. infestans isolates. The impacts of the four methods on the virulence of the four P. infestans isolates were isolate-specific. For isolates YF3 and 64093, all four methods were suitable for maintaining their virulence. Whilst for isolate HQK8–3, the rye seed and sterile water methods were more suitable to maintain its virulence than the other two methods. For isolate 32835, storage under mineral oil was the best method for maintaining its virulence. In view of these results, it is recommended P. infestans should be stored by several different storage methods to ensure the safety and stability of the isolates.

A gold nanoparticle-based lateral flow biosensor for sensitive visual detection of the potato late blight pathogen, Phytophthora infestans

Phytophthora infestans, the causal agent of late blight in potatoes and tomatoes, is the most important and ongoing pathogenic threat to agricultural production worldwide. Rapid and early identification of P. infestans is an essential prerequisite for countering the further spread of infection. In this study, a novel method for visual detection of P. infestans has been developed by integrating universal primer mediated asymmetric PCR with gold nanoparticle (AuNP)-based lateral flow biosensor. We employed asymmetric PCR to generate large amounts of single-stranded DNA (ssDNA) by amplifying a region of P. infestans-specific repetitive DNA sequence. The ssDNA products were then applied to the lateral flow biosensor to perform a visual detection using sandwich-type hybridization assays. In the presence of target DNA, sandwich-type hybridization reactions among the AuNP–probe, target DNA and capture probe were performed on the test line of the biosensor, and then a characteristic red band was produced for the accumulation of AuNPs. Quantitative analysis obtained by recording the optical intensity of the red band demonstrated that this biosensor could detect as little as 0.1 pg μL−1 genomic DNA. Furthermore, the specificity of the biosensor was confirmed by detecting three other Phytophthora species and two pathogenic fungi. We believe this method has potential application in early prediction of potato late blight disease and instigation of management actions to reduce the risk of epidemic development.

Development and validation of IPM strategies for the cultivation of cisgenically modified late blight resistant potato

Potato late blight disease remains the primary stressor of commercial potato production across the EU, typically requiring >10 fungicide applications per growing season to offset crop losses. In response, the goal of this study was to test and validate a novel, more durable, control strategy for potato late blight. This IPM2.0 strategy is based on the principles of Integrated Pest Management (IPM) which sees the deployment of a late blight resistant potato genotype, a cisgenically modified, Desiree based resistant potato line here, in conjunction with pathogen population monitoring for virulence to the resistance genes (R genes) deployed and a “do not spray unless”, low input fungicide spray strategy. Field evaluations were completed in the Netherlands and in Ireland in 2013, 2014 and in Ireland in 2015. Comparators used in this study included the original but susceptible potato variety Desiree and the conventional but highly resistant variety Sarpo Mira. The novel IPM2.0 strategy was compared to local common practice (fungicide applications on a near weekly basis) and an untreated control. Overall, the IPM2.0 control strategy validated here reduced the average fungicide input by 80–90% without compromising control efficacy. Corresponding environmental side-effects were reduced proportionally. The results underline the pragmatic role host resistance can provide to commercial potato production systems and to society at large if employed as part of an integrated late blight control system.

Prediction of miRNA and Identification of their Relationship Network Related to Late Blight Disease of Potato.

Late blight is a serious disease in potato caused by Phytophthora infestans. To date only few miRNA have been discovered which are related to late blight disease of potato during host pathogen interaction. Recent studies showed that miRNA, an important gene expression regulator, plays a very important role in host-pathogen interaction by silencing genes either by destructing or blocking of translation of mRNA. Homology search was performed between non-redundant mature miRNA sequences from miRBase database and Solanum tuberosum EST sequences from NCBI database. Screening of the potential miRNA was done after secondary structure prediction. The target related to late blight disease of respective miRNA was functionally annotated. To identify the relationship between the predicted and mature miRNAs, multiple sequence alignment and evolutionary relationships were established. 34 Candidate miRNA related to late blight disease of potato were identified which were associated to five target genes. These miRNAs were linked with Avr3a, INF1, INF2b genes which are elicitin like protein and triggers a hypersensitive response to host cell. Mapping of target sequences showed similarity with Solanum lycopersicum NRC1 gene of chr.1, which are reported as a casual protein required for Pto-mediated cell death and resistance in N. benthamiana. NRC1 are considered as a RX-CC_like domain-containing protein which shows similarity with coiledcoil domain of the potato virus X resistance protein (RX) in Solanum tuberosum. RX recognizes pathogen effector proteins and triggers a response that may be as severe as localized cell death thereby providing resistance against potato virus X.

Two different R gene loci co-evolved with Avr2 of Phytophthora infestans and confer distinct resistance specificities in potato.

Late blight, caused by the oomycete pathogen Phytophthora infestans, is the most devastating disease in potato. For sustainable management of this economically important disease, resistance breeding relies on the availability of resistance (R) genes. Such R genes against P. infestans have evolved in wild tuber-bearing Solanum species from North, Central and South America, upon co-evolution with cognate avirulence (Avr) genes. Here, we report how effectoromics screens with Avr2 of P. infestans revealed defense responses in diverse Solanum species that are native to Mexico and Peru. We found that the response to AVR2 in the Mexican Solanum species is mediated by R genes of the R2 family that resides on a major late blight locus on chromosome IV. In contrast, the response to AVR2 in Peruvian Solanum species is mediated by Rpi-mcq1, which resides on chromosome IX and does not belong to the R2 family. The data indicate that AVR2 recognition has evolved independently on two genetic loci in Mexican and Peruvian Solanum species, respectively. Detached leaf tests on potato cultivar ‘Désirée’ transformed with R genes from either the R2 or the Rpi-mcq1 locus revealed an overlapping, but distinct resistance profile to a panel of 18 diverse P. infestans isolates. The achieved insights in the molecular R – Avr gene interaction can lead to more educated exploitation of R genes and maximize the potential of generating more broad-spectrum, and potentially more durable control of the late blight disease in potato.

Management of late blight of Potato by Cyazofamid 34.5 SC + Mancozeb 64 WP

Experiments were conducted at Horticulture Research Station, Ooty to find the effect of new fungicide, Cyazofamid 34.5 SC + Mancozeb 64 WP on late blight disease of potato. The new fungicide mixture reduced the late blight incidence to the extent of 78.1% at 200 g/ha and was at par with the disease reduction observed (74.8%) when it was used at 1500 ml/ha. Hence, it is concluded that Cyazofamid 34.5 SC + Mancozeb 64 WP can be effectively be used for management of late blight disease in potato

Effect of Varieties and Fungicides on Potato Late Blight (Phytophthora infestans, (Mont.) de Bary) Management

Late blight of potato which is caused by Phytophthora infestans, (Mont) de Bary is an important disease of potatoes (Solanum tubersolum) and is a prevalent disease in all potato producing areas of Ethiopia. A field experiment was conducted for two consecutive years (2016 and 2017) under the main rainy season to develop integrated management options for late blight disease of potato at Bursa District, Sidama Zone, SNNPRS, Ethiopia. Two improved varieties having different level of resistance, four registered fungicides, and two unsprayed plots (control) were arranged in a factorial randomized complete block design with three replications. The result showed that all fungicides significantly reduced the infection of late blight as compared to the unsprayed treatments at both seasons. Two way interaction of variety by fungicide showed significant difference on controlling disease severity and increasing tuber yield in 2017. Fungicides Matco (Metalaxyl-8%+Mancozeb-64%) and Boss (Metalaxyl+Mancozeb) 72% WP significantly reduced severity of the disease as compared to Bacticide (Copper Hydroxide) and Mancozeb (Diathane-M45) in 2017 cropping season. Whereas in 2016 the disease pressure was low as the result there was no significant difference between fungicides. Depending on the fungicides efficacy and varietal reactions to the disease (21.82 to 30.47 t ha-1) and (20 to 36.84 t ha-1) tuber yield were obtained from the sprayed plot in 2016 and 2017, respectively. On the other hand from unsprayed plots, 10.63-18.63 t ha-1 and 8.8-17.4 t ha-1 tuber yield was obtained in 2016 and 2017 cropping seasons respectively. The mean yield advantage of fungicide sprayed plots for both varieties was 62% as compared to the unsprayed ones. The study confirmed that host resistance level and fungicide efficacy played an important role in host–pathogen–fungicide interaction to reduce the severity of late blight on potato. Therefore, it was confirmed that the combined effects of growing moderately resistant cultivars with the application of fungicides Matco at two spray frequency in 10 day intervals reduced the yield loss and damage caused by late blight even under high late blight pressure.

Using Cloud IOT for disease prevention in precision agriculture

The application of decision support system (DSS) for potato late blight disease prevention has proven its benefit. In fact the DSS permits efficiency, minimizes cost and environment impact by estimating the exact requirement fungicide quantity to apply. This prediction using weather condition based late blight forecast model. The required weather information is collected from costly weather station or imprecise historical data. However, with the emergence of the IOT, huge number of low cost and low power sensors nodes can easily be deployed in farmlands in order to gather a precise climate data. Moreover, the collected data can be forwarded by Internet connection to the so called cloud IOT framework. In this paper we present a new prototype of late blight prevention decision support system based on sensor network and cloud IOT.

Two orthologs of late blight resistance gene R1 in wild and cultivated potato

The R1 gene for resistance to oomycete Phytophthora infestans (Mont.) de Bary, the causal agent of late blight disease of potato (Solanum tuberosum L.), was initially identified in S. demissum and potato varieties bred by introgressing the S. demissum germplasm. Later a sequence characterized amplified region (SCAR) marker R1-1205 of this gene was also found in S. stoloniferum and S. polytrichon. Here we describe the full-length R1 sequence cloned from S. stoloniferum. This sequence is translatable, and this evidence of structural gene integrity is reinforced by functional characterization of the S. stoloniferum R1 gene in an effectoromics experiment. When screened across a series of S. demissum and S. stoloniferum accessions, the R1 sequences differed by several single nucleotide polymorphisms and an indel; this indel served the basis for constructing SCAR markers R1-517 and R1-513 that reliably discerned two R1 orthologs. The demissum-specific marker R1-517 was found in all S. demissum accessions under study; it was also present in many demissum-derived potato varieties and hybrids. The stoloniferum-specific marker R1-513 was found in 27% of S. stoloniferum and S. polytrichon accessions; however, we failed to discern this marker in the genotypes of cultivated potato listing S. stoloniferum in their pedigrees. Most probably, such absence of R1-513 is best explained by an opportunistic breeding history of stoloniferum-derived founder lines, which were employed first and foremost in breeding for resistance to potato virus Y: eventually, these founder lines are devoid of the R1 gene.

Eco-friendly management of late blight of potato– A review

Late blight of potato caused by fungus Phytophthora infestans responsible for Irish famine in the year 1845, is one of the most dramatic episode caused by plant pathogen in human history. One million people died due to famine in Ireland. So eco-friendly management of potato late blight disease is a necessary goal to be accomplished.During last many years, management strategies solely relied upon the application of fungicides due to rapid development of late blight epidemics. However, indiscriminate use of fungicide posesses a serious threat to the environment and human health. It is also responsible for built up of resistance in the pathogen and have adverse effect on beneficial organisms such as nitrogen fixers, resident antagonism and mycorrhizal fungi. So to minimize the fungicide use, eco-friendly means for late blight management are required on a priority basis. In recent years, significant changes in isolates of late blight fungus have been recorded including changes in aggressiveness to the crop also. Since, late blight is a community disease so, effective eco-friendly management must be adopted by the all producers, farmers, gardeners and growers with the help of government agencies, extension specialist and crop consultants etc. The strategy to control late blight is the prevention of establishment of Phytophthorainfestans in potato crop. In this context, disease management by cultural practices is the first line of defense while forecasting system, physiological strategies, biological control, host plant resistance and bio-technological approach are essential for efficient, effective and eco-friendly management of late blight of potato.

MANAGEMENT OF POTATO LATE BLIGHT THROUGH HOST PLANT RESISTANCE AND FUNGICIDE USE IN SOUTH OMO ZONE, SNNPR, ETHIOPIA

The study was carried out in April 2015 at South Ari district, Senmamer kebele of South Omo Zone Southern Nation Nationality People Regional State to test and demonstrate the effects of integrating host resistance and fungicide application for management of potato late blight disease. In this experiment one relatively late blight resistance improved Irish potato variety (Belete) was collected from Holleta Seed producer Association and susceptible local control potato varieties were used. RCBD with four replications (farmers as replication) were used. A recommended rate of CurzateR R WP fungicide was applied while susceptible local variety developed the first blight symptom. GLM procedures were followed to analyze yield, disease incidence and severity. LSD (P<0.01) values were used to separate treatments mean. Total weight of tubers per plot (kg) was show significant difference (P<0.01) among treatments. The highest total weight of tubers per plot (kg) was given by treated belete (T1) (22.625) followed by untreated belete (T3), untreated local (T4) and treated local (T2) (18.525, 11.875and 10.125) respectively (Table 2). Local potato variety also gave the highest unmarketable tubers weight per plot. The result indicated that there were a significant difference (P<0.01) and (P<0.05) among treatments on late blight incidence and severity respectively. Untreated local variety (T4) showed highest late blight incidence and severity as compare to treated belete variety (T1). The experiment result suggested that application CurzateR R WP fungicide twice on variety belete results in significant reduction on late blight progress, with a corresponding increased tubers yield.

The Impact of Steroidal Glycoalkaloids on the Physiology of Phytophthora infestans, the Causative Agent of Potato Late Blight.

Steroidal glycoalkaloids (SGAs) are plant secondary metabolites known to be toxic to animals and humans and that have putative roles in defense against pests. The proposed mechanisms of SGA toxicity are sterol-mediated disruption of membranes and inhibition of cholinesterase activity in neurons. It has been suggested that phytopathogenic microorganisms can overcome SGA toxicity by enzymatic deglycosylation of SGAs. Here, we have explored SGA-mediated toxicity toward the invasive oomycete Phytophthora infestans, the causative agent of the late blight disease in potato and tomato, as well as the potential for SGA deglycosylation by this species. Our growth studies indicate that solanidine, the nonglycosylated precursor of the potato SGAs α-chaconine and α-solanine, has a greater physiological impact than its glycosylated forms. All of these compounds were incorporated into the mycelium, but only solanidine could strongly inhibit the growth of P. infestans in liquid culture. Genes encoding several glycoside hydrolases with potential activity on SGAs were identified in the genome of P. infestans and were shown to be expressed. However, we found no indication that deglycosylation of SGAs takes place. We present additional evidence for apparent host-specific adaptation to potato SGAs and assess all results in terms of future pathogen management strategies.

Risk Management Strategies using Precision Agriculture Technology to Manage Potato Late Blight

Core Ideas The benefits of adopting precision farming technology was investivated in scheduling fungicide applications to manage potato late blight. The precision farming technology is the preferred method to schedule fungicide applications in terms of disease suppression, net return per 0.41 ha, and risk‐adjusted net return. The increased adoption of the precision farming technology would help manage late blight, limit potential crop losses, and improve net returns. Precision agriculture has emerged as a revolutionary technology, which transforms farming related data into useful information for agricultural decision‐making. This paper compares precision farming technology with calendar‐based approach in scheduling fungicide applications to manage potato (Solanum tuberosum L.) late blight disease. Three fungicide scheduling strategies were evaluated: calendar‐based strategy, BlightPro decision support system based strategy (DSS‐based strategy), and unsprayed control. Using results from 14 yr of computer simulation experiments for 59 locations in the United States, we constructed distributions of net return to all costs excluding fungicide cost and application cost per 0.41 ha (net return per 0.41 ha) for the calendar‐based and DSS‐based strategies at each location. These distributions were then compared using three risk management methods: stochastic dominance, stochastic dominance with respect to a function, and stochastic efficiency with respect to a function. The DSS‐based strategy was identified as the most effective approach to manage late blight in terms of disease suppression, net return per 0.41 ha, and risk‐adjusted net return. Results indicate that the DSS‐based strategy is the preferred method to schedule fungicide applications. Under high disease pressure circumstances, the economic benefits to potato growers of adopting the precision agriculture technology ranged from US$30 to $573 per 0.41 ha. For risk neutral individuals, who are concerned about the difference between average net return per 0.41 ha, the benefits ranged from $30 to $305 per 0.41 ha. Except for growers raising the moderately resistant potato cultivars, more risk averse individuals tended to benefit more from adopting the precision agriculture technology, with benefits ranging from $38 to $573 per 0.41 ha.

EVALUATION OF SOME COMMERCIAL FUNGICIDES FOR CONTROLLING LATE BLIGHT DISEASE OF POTATO IN EGYPT

Nowadays, the successful management of potato late blight disease under Egyptian conditions requires evaluating the effectiveness of fungicides continuously. A total of 419 isolates of Phytophthora infestans were isolated during three growing seasons in Egypt. Under laboratory conditions, all active ingredients treatments significantly reduced the mycelium growth compared to the untreated control plates. Cymoxanil and Dimethomorph have the highest effect on the mycelium growth reduction. Results obtained from the field experiment showed that fungicides contain mixtures of active ingredients were superior in their effect than other fungicides which contain only one active ingredient. In addition, fungicides contain mixture of contact with trans- laminar active ingredients reduced potato late blight incidence more than contact fungicide with one active ingredient. Triomax has the highest effect on foliar blight reduction.